Liquid Crystal Medium for Narrow Bezel PSA Displays
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Solution Overview
Problem
Current liquid crystal display technologies face challenges such as strong viewing-angle dependence of contrast in TN LCDs, reduced reliability due to polyimide alignment layers, and issues with sealant diffusion and curing in the one drop filling process, leading to edge mura and reduced display performance, especially in narrow bezel designs.
Innovation Solution
A liquid crystal medium comprising specific compounds with formulae I to V, which provide improved compatibility with the one drop filling process, reduce edge mura, and enhance display reliability by minimizing interaction with sealant components, while allowing for narrower bezel designs with reduced rotational viscosity and increased clearing temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional liquid crystal media are used in narrow bezel displays with one drop filling process, then sealant diffusion occurs during curing, but this leads to edge mura and reduced display quality
Solution Approach 1:
The patent introduces a liquid crystal composition as an intermediary medium that is chemically incompatible with sealant components. This composition acts as a barrier that prevents sealant diffusion into the display cavity during the curing process, thereby eliminating edge mura while maintaining narrow bezel design requirements
Solution Approach 2:
The patent modifies the chemical composition parameters of the liquid crystal medium by incorporating specific compounds (cyclic carboxylic acid derivatives and their esters) that alter the interaction properties with sealant materials. This parameter change transforms the liquid crystal from a vulnerable medium to one that actively resists sealant diffusion
2Manufacturing precision
If polyimide alignment layers are used to achieve uniform LC molecule alignment, then alignment quality improves, but reliability decreases due to interaction with liquid crystal components
Solution Approach 1:
The patent extracts and eliminates the polyimide alignment layer from the display structure. Instead of using polyimide, the invention employs alternative alignment methods or materials that do not interact adversely with the liquid crystal composition, thereby maintaining alignment quality while improving long-term reliability
Solution Approach 2:
The patent replaces the polyimide alignment layer with a functional equivalent that achieves the same alignment purpose without the harmful interactions. This could be through photoalignment layers or self-aligning liquid crystal compositions that replicate the alignment function of polyimide without its reliability issues
3Productivity
If the one drop filling process is used to reduce manufacturing complexity, then productivity improves, but sealant diffusion and curing issues arise
Solution Approach 1:
The patent prepares the liquid crystal composition in advance with specific chemical properties (incorporating cyclic carboxylic acid derivatives and esters) that cushion against potential sealant diffusion during the one drop filling process. This pre-engineering of the composition ensures compatibility and prevents defects before manufacturing occurs
Solution Approach 2:
The patent creates a composite liquid crystal composition by combining multiple components (cyclic carboxylic acid derivatives, esters, and other liquid crystal materials) that work synergistically. This composite material maintains the benefits of one drop filling while adding resistance to sealant diffusion and improving overall display reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed liquid crystal medium achieves reduced edge mura, improved reliability, and enhanced display performance, including low rotational viscosity and broad nematic phase range, suitable for polymer-stabilized displays with narrow bezel designs, particularly in TV and monitor applications.
Implementation Method 1
OCB ('optically compensated bend') displays are known which are based on a birefringence effect
Implementation Method 2
The LC medium usually has a negative dielectric anisotropy. On application of an electrical voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place
Data Source
AI summary
The present invention relates to a liquid crystal (LC) medium optionally comprising a polymerisable compound, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in an LC display of the polymer sustained alignment (PSA) type, and to an LC display, especially a PSA display, comprising it, especially to an LC display with narrow bezel.